Asphalt manufacture

ABSTRACT

An asphalt flux having improved rheological properties is prepared from a straight run asphalt residue by means of catalytic hydrogenation under moderate conditions.

United States Patent [191 McClaren et al.

ASPHALT MANUFACTURE Inventors: Gordan A. McClaren, Houston,

Tex.; John W. Gibson, Oakland.

Calif.

Assignee: Shell Oil Company, New York, NY.

Filed: May 19, 1971 Appl. No.: 144,950

Related US. Application Data Continuation-impart of Ser. No. 880,629, Nov. 28 I969, Pat. No. 3,607,722.

us. a. 208/44 Int. Cl C106 3/02 Field of Search 208/44 m1- 3,755,139 [451 Aug 28, 1973 [56] References Cited UNITED STATES PATENTS 3,258,419 6/l966 Hanson 208/44 3.607.722- 9/1971 McLaren et al.

Primary Examiner--Delbert E. Gantz Assistam Examiner-Veronica OKeefe Attorney-Leonard P. Miller and Glen R. Grunewald 57 ABSTRACT PATENTEUmcea I973 SLOPE Y SLOPE X IOOO IOO IOOO SAYBOLT SECONDS FUROL VISCOSITY AT 275F INVENTORSI G. A. Mc LAREN THEIR AGENT 1 ASPHALT MANUFACTURE CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of US. ap-

plication Ser. No. 880,629, filed Nov. 28, 1969, now

This invention relates to a process for producing asphalt products having highly desirable rheological properties from asphaltic pitch by means of catalytic treatment with hydrogen.

Conventional asphalt manufacture involves the reduction of soft straight-run residues, typically having penetrations above 1000 decimillimeters (dmm) at 77F, to a consistency permitting their use as asphalt products by vacuum flashing, solvent extraction or air blowing at an elevated temperature. In the first two of the aforementioned procedures, reduction to specification grade is accomplished by removing a proportion of the heavy oil fraction contained in the straight-run residue. In the latter process the desired consistency is obtained through condensation and polymerization of the heavy oil and resinous fractions contained in the residues.

Because the heavy distillate oil fraction contained in straight-run residue is valuable, for example, as conversion feed for catalytic cracking, there has been an increasing trend toward reducing these residues to a hard asphaltic pitch thereby maximizing distillate oil recovery. The resulting pitches are usually hard, relatively brittle materials, having very low penetrations, e.g., 5 dmm or less at 77F. Due to their inherent physical properties, such pitches have limited utility and are not suitable for most asphaltic applications unless blended with a cutter-stock such as a flashed distillate or other oil. Obviously, the use of such an oil or oil-containing residue for blending, frustrates the objective of maximizing the recovery of valuable oil fractions from the residue. Hard pitch can be disposed of by conversion to coke for use as fuel, but this likewise is not a very satisfactory alternative, since pitch residues frequently contain high concentrations of sulfurous and nitrogenous compounds which when bumed result in the release of noxious sulfur and nitrogen oxides to the air.

Therefore, there exists in the art a need for a practicable method of converting asphaltic pitches to useful products. The present invention provides such a process; a process wherein asphalt products are prepared having rheological properties superior to those of asphalts prepared from straight-run residues by conventional methods of manufacture.

SUMMARY OF THE INVENTION It has now been found that asphalt products having highly desirable rheological properties can be prepared from asphaltic pitch by means of catalytic hydrogenation under moderate conditions. Hydrogenation under the conditions hereinafter described has been found to alter the chemical and physical characteristics of the pitch in such a manner as to produce products having viscosimetric properties superior to those of asphalts prepared by conventional manufacturing techniques. In addition, it has been found that good product yields are attained at relatively low levels of hydrogen consumption, and that good catalyst life can also be achieved. This latter aspect is particularly surprising considering the chemical nature of pitch, which in addition to containing a substantial proportion of asphaltenes that would be expected to deposit on the catalyst, also contains sizable quantities of sulfur and nitrogen compounds, and metals such as vanadium and other elements considered to be detrimental to catalyst life.

As an additional benefit of the present process, concomitant distillate products are freed of a substantial proportion of heteroatoms and trace metals. Since sulfur and nitrogen compounds and metalliferous contaminants are relatively innocuous in asphalt, it is preferred to only partially remove these contaminants from the residue. Metal deposition on catalyst is thus limited thereby extending catalyst life.

DETAILED DESCRIPTION OF THE INVENTION The rheological properties of asphalt are generally expressed in terms of their penetration, viscosity, softening point and ductility. These properties are consid ered indicative of the nature of the asphalt and are related to the inherent structure of bituminous materials. Asphalts of equivalent penetration grade are not necessarily suitable for the same application, sin'ce penetration is but one measure of the asphalts rheological properties. For example, it is known that penetration together with viscosity'can be used to predict the setting properties of asphalt when hot-mixed with aggregate in paving applications. It has been found through experience that asphalts of equivalent penetration grade will set slower or-faster depending on their vis'-' cosity. Generally those having the highest viscosity at or near the hot-mix temperature will have the fastest setting time and thus be the more advantagous for actual use.

A highly significant advantage of the present invention is that for a given penetration, the asphalt products prepared by the inventive procedure, have appreciably greater viscosities than those produced directly from straight-run residue by conventional vacuum flashing. The catalytic hydrogenation of the pitch apparently results in a molecular rearrangement which not only increases its penetration without the use of cutter-stocks, but additionally imparts highly desirable viscosimetric properties to the resulting asphalt products.

The improved viscosimetric properties of asphalts prepared in accordance with the invention will be more readily apparent by reference to the accompanying drawing. The drawing is a graph showing the relationship between penetration and viscosity of asphalts prepared by conventional vacuum flashing of a straightrun residue (Slope X), compared with the penetrationviscosity relationship of asphalts prepared by catalytic hydrogenation of pitch (Slope Y) derived from the same straight-run residue. It is evident from the graph, that at most any given penetration the viscosity at 275F of the asphalt prepared by vacuum reducing to grade, is lower than that of the asphalt prepared by the process of the invention, e.g., a penetration grade asphalt produced by the present process has a viscosity at 275F of I30 SSF as compared to a viscosity of only SSE for the asphalt obtained by reducing straightrun residue to a 90 penetration grade. The hydrogenated product would, therefore, set faster and be more desirable in paving applications than the conventionally prepared asphalt.

The starting material or feedstock to the process of the invention can be any asphaltic residue of petroleum, e.g., cracked residue, straight-run residue (bottoms product from the atmospheric or vacuum distillation of crude oils), residue from solvent deasphalting processes and the like. Such residues comprise predominantly high boiling fractions, i.e., those fractions boiling above 650F, of which the asphaltic (pitch) fraction generally comprises the highest boiling materials therein. Such asphaltic pitch-containing residues can be catalytically hydrogenated directly and the improved asphaltic pitch fraction subsequently recovered by fractionation, or if desired the residue can be fractionated prior to hydrogenation to recover the distillate fraction beforehand, in which case the feed to the process will be predominantly the heavy pitch fraction.

Lower boiling hydrocarbon fractions can be included in the asphaltic residue feed if desired and in some cases can be quite advantageous as the low boiling fractions tend to be a wash oil in the catalytic hydrotreatment and would be improved in quality, e.g., through partial removal of sulfur and nitrogen compounds. The process of the invention is particularly advantageous in preparing asphalt products from hard asphaltic pitch, i.e., pitch having a penetration below about 5 dmm at 77F as determined by ASTM Method D5, and boiling point essentially above about 900F. Such pitch is obtained, for example, by deep flashing straight-run or cracked residue.

Another advantageous application of the invention is in preparing an asphalt flux, suitable for processing into a variety of useful products, from a straight-run residue obtained from crudes which normally do not have utility in this respect. For example, straight-run asphalt residues obtained from California and certain heavy Venezuelan crudes and generally not suitable for use in preparing roofing flux because upon air blowing of the vacuum flashed residues from such crudes to the requisite softening point, a hard asphalt having a penetration of 0-7 dmm is formed which is well below the 16-22 dmm penetration typically specified for roofing materials. The use of less severe vacuum flashing or the addition of cutter stocks, while effective in increasing the penetration of the flux, adversely affects other properties of the blown product such as softening point and spread-of-flame test properties, hence the product is still unsuitable.

However, it has been found that if the straight-run residue is hydrotreated under the previously specified ing fraction in the straight-run residue feed. Preferably the flux product will have a penetration at 77F of about 250 to 600 dmm, more preferably from 250 to 500 dmm. The desired flux product is normally obtained with relatively low conversion to lower boiling hydrocarbons, e.g., generally less than %w and usually less than 10%w of the straight-run residue feedstock is converted to products boiling below 600F. In

lated industrial fluxes, coatings and saturants, and has also been favorably employed as a blending component for paving asphalts. Thus, the present process offers a means of converting straight-run residues of the type which normally have very limited utility in the production roofing materials and related products, into a multipurpose flux suitable for preparing a broad range of asphalt products.

Catalytic hydrogenation processes in general, are well known and thoroughly described in the art, and need not be discussed in detail herein. In accordance with the invention an asphaltic residue feedstock is subjected to catalytic treatment with hydrogen at temperatures ranging from about 600F to about 850F, preferably from about 675F to 775F, and at pressures of about 1,000 psigto about 5,000 psig, preferably 1,500 psig to about 3,500 psig. The weight hourly space velocity can be varied from about 0.2 to about 2.0, but preferably is maintained at about 0.5 to about 1.0. A hydrogen circulation rate of between about 1,500 and 15,000 SCF/bbl of pitch can be employed, more normally from about 5,000 to 10,000 SCF/bbl of pitch.

Under the specified hydrogenating conditions, generally less than about l5%w, and normally less than about l0%w of the feedstock is converted to products boiling below 600F to obtain relatively high yields of asphalt. If desired, somewhat higher conversions to light boiling products can be obtained which are recoverable and could suitably be used for distillate fuels, jet fuels or other purposes.

Effluent from the catalytic hydrotreating zone is separated into one or more fractions. For example, a gas phase is separated from the liquid product and desirably is recycled to the hydrotreating zone, with or without a suitable treatment to remove any undesirable impurities such as hydrogen sulfide or ammonia. Makeup hydrogen can be added as needed. Pure hydrogen is not necessary as gases rich in hydrogen can be used, e.g., hydrogen gases produced in catalytic reforming of naphthas which are on the order of -80%v by volume of hydrogen or more, but correspondingly higher operating pressures are required to maintain adequate hydrogen partial pressures.

Liquid product from the hydrotreating zone is suitably fractionated to remove any low boiling hydrocarbons and to recover an asphalt fraction boiling essentially above about 600F, and preferably above about 700F, and having a penetration at 77F of at least about 20 dmm higher and preferably at least 40 dmm higher than the corresponding asphaltic fraction in the residue feed. Thus by practice of the invention asphalt products of most any desired penetration can be prepared from asphaltic pitch or pitch containing residues. In a preferred embodiment of the invention hard pitch having a penetration at 77F of less than about 5 dmm is converted to asphalt products having penetrations of about 30 to about 500 at 77F and viscosities between about 50 and about 500 centistokes at 275F.

In general, any of the catalysts conventionally employed in the hydrogenation of heavy petroleum oils can be utilized in the present process. Such catalysts generally comprise a hydrogenation component on a suitable refractory oxide support. Examples of suitable catalytic components are the Group VIB and Group VIII metals such as molybdenum, tungsten, chromium, cobalt, nickel, iron and their oxides and sulfides. Mixtures of these materials or compounds of two'ormore of the oxides can also be employed. These catalytic components are generally composited, with a suitable carrier of the solid refractory type, e.g., alumina, silica, or combinations thereof. Supports having'an acidic character such as silica alumina or fluorided alumina are also suitable. Especially suitable are the oxides and /or sulfides or nickel and molybdenum on'an alumina carrier. The metals are generally employed in an amount ranging from-about 0.1%w to about'=25%w-or higher.- The preparation of hydrogenation catalysts is" well known and practiced commercially;

The invention will be furtherdescribedby means of thefollowing examples which demonstrate various embodiments of the invention. It should be understood, however, that these examples are given for illustrative purposes only and that the invention in its broader aspects is notlimited thereto.

EXAMPLE I Flasher pitch having the properties indicated in Table I was hydrogenated in'the presence of a cornmerical hy drogenation catalyst under the conditions shown in Table II. The totalliquid product from'each of these TABLE I Pitch Feedstock Source Vacuum Flashed Strai t-Run Residue of a Heavy an Joaquin Valley, California Crude Properties Penetration at 77F, dmm 0-1 Viscosity at 275F, cs I900 Softening Point, "F I77"F Com nents boiling above 932. ,-%w 99.4 Sulfur, law 1.6 Nitrogen, %w I .5 Oxygen, %w H lron, pm 195 Nicke ppm 215 Vanadium, ppm 105 TABLE II I II III IV h drogenating onditions catal t Age (l), ays 64 69 74 8S temperature, "F 725 738 752 770 pressure, psig I800 I800 I800 I800 weight hourly space velocitfi 0.69 0.5 9 0.6! 0.43 Ratio ,lpitch, scflbbl 7,400 9,300 I 1,800 8,000 H, consumption, scf/bbl 350 410 510 830 total liquid product kw yield basis feed 98.8 98.8 97.8 98.9 kw product boiling I below 572"! 2.3 3.2 5.0 9.3 kw product boiling above 932F 89.9 85.9 82.9 70.9 properties of 572F plus asphalt product penetration at V I 77F, dmm 40 78 I00 470 viscosity at 275F, cs 415 270 216" 86' viscosity at I40F, 1 poise: 4,090 1,545 1,040 136 %w yield basis total liquid product 98.21 97.70 96.46 93.36 removal'of Heteroatoms, kw Y Sulfur 47 S7 55 1 66 Nitrogen 8 9 3 I2 20 Oxygen 49 53 58 59 metalsrernoval from total product,%w Iron 92' 1 87 a Nickel 65 57 i 64': Vanadium 47 67 68 (I) l/l6' inch' extruded pellets of alumina-supported nickelmolybdenum,"3%'nickel, l0%molybde'num was'employedas'cattlly'st.

From the-above data it is evident that useful {asphalt products can be manufactured from" .pitch without the Y abovedatafurthei' demonstrate that virtually theenti re range of asphalt consistencies can'bep'rodu'ced bycatalytichydrotreatment of pitches, e.g., from'low'penetrationgrade asphalts to soft fluxes. Theresponse to penetration-increase has been found to be more'strongly dependent on'temperature of the catalytic hydrotreatment than on pressure; By-modifying wthe hydro'gena' tion temperatureand controlling theother variables, asphalt products of most any desired consistency can be obtained. g

It is noted that thecatalyst after'85 days still possessed activity 'indicating such a catalyst can be effectively employed in'thetreatment of heavyasphaltic charge stocks for relatively long periods of service.

EXAMPLE n i To further demonstrate the inventive process, asphalts of varying consistencies were prepared under the conditions and having the properties shown in Table III. The feedstock was theme as that of Example I.

EXAMPLE Ill Straight run residue obtained from a 60 percentCalifomia/40 percent Alaska crude was hydrogenated in D the presence of the same catalyst employed in Example I under the conditions'shown in Table V. The total liquid product from Run IX and X was'vacuumdistilled:

to remove fractions boiling below'90 IF and 932F respectively. The properties of the asphalt fluxes thereby obtained are compared to the properties of a corre-' sponding boiling fraction of unh ydrotreated straight run residue and also to a typical premium coating flux (PCF) prepared from a Venezuelan crude (identifired in Table IV as Lagomar PCF).

TABLE IV Unhydro treated straight- Lagomar' IX X run res. PCF

Hydrotreating conditions Temperature, F 734 726 Pressure, psig I800 l8000 1 Liquid Hourly space velocity 0.50 0.50 Properties of Flux Boiling point, F 90! 932 932 857 Softening point, "F 8l 84 129 90 Penetration at 77Fdmm 500(l) 400(1) 36 350(l) (1) Calculated from the viscosity and softening point.

The above data indicate that hydrotreating of a straight-run asphalt generally considered unsuitable for preparing roofing materials and similar products, efl'ectively increases the penetration and modifies other characteristics of the asphalt so as to produce an asphalt flux having properties similar to a premium coating flux of the type typically employed in preparing roofing materials, coatings, saturants, etc.

EXAMPLE IV To illustrate the utility of asphalt flux obtained in accordance with the invention in preparing asphalt coatings, the products of Run IX and X were blown with air under the conditions shown in Table V. The properties of the blown products were compared to a coating prepared by air blowing the premium coating flux shown in Table IV. Typical specifications for coatings of this type require softening points of from 215 to 222F and penetrations at 77F of from 15 to 25 dmm.

TABLE V Typical PCF IX X Lagomar Blown Run Conditions Temperature, F 475 475 475 rate of air flow, ft air/min 0.5 0.5 0.5 Charge, k 6 6 6 Time to 2 F softening point, hrs. 5.3 6.9 4.0-4.5 Properties of coating Penetration at 77"F, dmm 2] l7 l8 Penetration Index 5.2 4.4 4.8 Oil Loss During Blowing, %w 0.8 1.1 0.4

EXAMPLE V To further illustrate the utility of the present process, the properties of two 90 penetration grade paving asphalts prepared from hydrogenated base materials were compared to a 90 penetration grade asphalt blended from unhydrotreated basestocks derived from the same source, i.e.,.a blend of 90 percent California/l0 percent Alaska crude. The results of this comparison (presented in Table VI) indicate that paving asphalts having low heptane-xylene equivalencies and which exhibit negative Oliensis Spot Tests can be prepared from asphalt basestocks which normally do not possess these desirable properties. The blown fluxes employed in preparing these blends were blown with air to a 220F softening point. Straight-run residue has been abbreviated as SRR.

TABLE VI l-leptane Xylene equivalent 24 hours Oliensis spot test 24 hours 240 Negative 20/80 Negative 20/80 152 Positive 35/65 (1) AASHO Method T-l02 (2) Califomia Test Method No. 325. This test is a modification of the Oliensis Spot Test and indicates the percentage of xylene that must be mixed with heptane to suppress the Oliensis spot.

Various modifications can be made in procedures of the specific examples to provide other embodiments which fall within the scope of the present invention. For example, it is possible to prepare penetration grade asphalts directly by blending the air-blown coating grade asphalts made from the hydrogenated fluxes with unblown hydrogenated flux or a three-component blend of air-blown hydrogenated flux, unblown hydrogenated flux and non-hydrogenated vacuum flasher pitch (or admixtures with unhydrogenated flux) to give a wide range of asphalt viscosities at a given penetration level both before and after an aging step.

We claim as our invention:

1. A process for producing an asphalt flux from a straight-run asphalt residue which comprises 1. contacting said straight-run asphalt residue with hydrogen in the presence of a hydrogenation catalyst at a temperature in the range of from about 600F to about 850F and a pressure of from about 1,000 to about 5,000 pounds per square inch gauge,

2. fractionating the hydrotreated liquid product obtained in step 1 to remove materials boiling below 840F, and

3. recovering an asphalt flux having a penetration at 77F at least 40 decirnillirneters higher than the corresponding boiling fraction in the straight-run residue feed.

2. The process of claim 1 wherein the catalytic hydrogenation is perfonned at a temperature in the range of from 675F to about 775C and a pressure of 1,500 to about 3,500 pounds per square inch gauge.

3. The process of claim 2 wherein the catalyst comprises nickel-molybdenum supported on alumina.

4. The process of claim 1 wherein the recovered asphalt flux is air blown to produce a coating grade asphalt having a softening point of 215 to 222F and a penetration at 77F of between l5 and 25 decimillimeters.

10 7. The process of claim 1 wherein recovered asphalt flux is air blown to produce a coating grade asphalt which is subsequently blended with a portion of the recovered asphalt flux or an unhydrogenated flux to produce a paving grade asphalt.

P0405) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION ma 3,755,139 Dated August 28,1973

Inventor) GORDON A. McLARENvand JOHN w. GIBSON I It is certified that'error appeers in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On first sheet ofpacent inventor's name should be corrected to read as Gordon1A. McLaren Signed and sealed this 19th day of February -197L (SEAL) I Attest:

EDWARD M.FLETCHER,JR. c. MARSHALL DANN Attesting --Offi cer Commissioner of Patents 

2. The process of claim 1 wherein the catalytic hydrogenation is performed at a temperature in the range of from 675*F to about 775*C and a pressure of 1,500 to about 3,500 pounds per square inch gauge.
 2. fractionating the hydrotreated liquid product obtained in step 1 to remove materials boiling below 840*F, and
 3. recovering an asphalt flux having a penetration at 77*F at least 40 decimillimeters higher than the corresponding boiling fraction in the straight-run residue feed.
 3. The process of claim 2 wherein the catalyst comprises nickel-molybdenum supported on alumina.
 4. The process of claim 1 wherein the recovered asphalt flux is air blown to produce a coating grade asphalt having a softening point of 215* to 222*F and a penetration at 77*F of between 15 and 25 decimillimeters.
 5. The process of claim 1 wherein less than 15 percent of the straight-run residue asphalt feed is converted to products boiling below 600*F.
 6. The process of claim 2 wherein the recovered asphalt flux has a penetration at 77*F of about 250 to 600 decimillimeters.
 7. The process of claim 1 wherein recovered asphalt flux is air blown to produce a coating grade asphalt which is subsequently blended with a portion of the recovered asphalt flux or an unhydrogenated flux to produce a paving grade asphalt. 